The invention relates to a laser treatment apparatus which irradiates a diseased part of a patient's eye with a treatment laser beam, thereby treating the diseased part of the patient's eye by means of photocoagulation or the like.
In order to treat a para fovea neovascularization formed in the vicinity of the central fovea and due to a disease in which the main lesion is choroidal neovascularization, such as age related macular degeneration, the laser treatment wherein the diseased part is irradiated with a laser beam so that the diseased part is photocoagulated is mainly employed. In this treatment, it is very important to determine the position of the central fovea so as not to affect the central fovea.
Conventionally, the position of the central fovea is determined while fixing the patient's eye to an aiming beam having a circular shape of about 50 .mu.m. Alternatively, the position of the central fovea is determined in the following manner. After an eye is fixed to an external fixation lamp attached to a slit lamp or the like, an aiming beam is moved (scanned) vertically and horizontally, and it is checked whether the aiming beam can be visually recognized or not.
However, the former method in which an eye is fixed to an aiming beam has a problem in that, since the spot size of the aiming beam is as small as about 50 .mu.m, an eye of a patient having reduced central visual acuity is unstably fixed to the beam, and hence the aiming beam is moved when the laser irradiation is conducted.
In the latter method, skill is required to correctly determine the position of the central fovea, and therefore it is often difficult to determine the position of the central fovea.